Detection of glutathione, cysteine, and homocysteine by online derivatization-based electrospray mass spectrometry

Homocysteine, hyperhomocysteinemia and H-type hypertension

Homocysteine (Hcy) is a sulfur-containing nonessential amino acid derived from the intermediate metabolites of methionine. Methionine is obtained from dietary proteins, such as poultry, meat, eggs, seafood, and dairy products. Abnormalities in Hcy metabolic pathways, deficiencies in dietary methionine, folate, and vitamins B12, B6 and B2 and genetic defects, polymorphisms, or mutations in Hcy metabolism-related enzymes may lead to an increase in plasma Hcy levels. Generally, a plasma Hcy level higher than 10 μmol/L or 15 μmol/L has been defined as hyperhomocysteinemia (HHcy). An individual with essential hypertension complicated with HHcy is considered to have H-type hypertension (HTH). Currently, HHcy is considered a novel independent risk factor for various cardiovascular diseases. To provide a useful reference for clinicians, the research progress on Hcy, HHcy and HTH in recent years was systematically reviewed here, with a focus on the source and metabolic pathways of Hcy, plasma Hcy levels and influencing factors, detection methods for plasma Hcy levels, relationship between Hcy concentration and hypertension, pathogenesis of HTH, cardiovascular complications of HTH, and treatment of HTH.

Applications of ambient ionization mass spectrometry in 2022: An annual review

The development of ambient ionization mass spectrometry (AIMS) has transformed analytical science, providing the means of performing rapid analysis of samples in their native state, both in and out of the laboratory. The capacity to eliminate sample preparation and pre-MS separation techniques, leading to true real-time analysis, has led to AIMS naturally gaining a broad interest across the scientific community. Since the introduction of the first AIMS techniques in the mid-2000s, the field has exploded with dozens of novel ion sources, an array of intriguing applications, and an evident growing interest across diverse areas of study. As the field continues to surge forward each year, ambient ionization techniques are increasingly becoming commonplace in laboratories around the world. This annual review provides an overview of AIMS techniques and applications throughout 2022, with a specific focus on some of the major fields of research, including forensic science, disease diagnostics, pharmaceuticals and food sciences. New techniques and methods are introduced, demonstrating the unwavering drive of the analytical community to further advance this exciting field and push the boundaries of what analytical chemistry can achieve.

Pulsed-post column derivatization coupled to green liquid chromatography for the determination of glutathione and cysteine based on thioacrylates formation

In the present work, we developed a method for the determination of thiols (cysteine and glutathione) in yeast samples under the new concept of Pulsed-post column derivatization (Pulsed-PCD). For the chromatographic separation of the analytes, 100% aqueous mobile phase was used and the eluted compounds reacted on-line with the injected pulses (100 μL) of the derivatizing reagent (ethyl propiolate + Britton-Robinson buffer). Spectrophotometric detection of the derivatives was carried out at 285 nm. The Pulsed-PCD configuration, the selection of the analytical column and the pulsed-PCD reaction conditions were investigated. The method was validated for the determination of endogenous content of the analytes in dry and fresh yeasts, with LODs of 3.0 μmol L^-1. The percent recovery ranged between 85.2 and 114.4% in all cases and the results were compared with a corroborative method based on classical PCD. The analytical greenness of the proposed method was evaluated using two tools; Analytical Eco-Scale and Green Analytical Procedure Index (GAPI). The greenness score of the HPLC-Pulsed-PCD method (score = 77) was compared with that of the corroborative HILIC-PCD method (score = 71) and was found to be greener in terms of the amount of chemicals used and the produced wastes.

Association between Micronutrients and Hyperhomocysteinemia: A Case-Control Study in Northeast China

Hyperhomocysteinemia (HHcy) is an independent risk factor for cardiovascular and cerebrovascular diseases where the plasma homocysteine (Hcy) concentration exceeds 15 µmol/L. HHcy is affected by vitamins B12, B6, and folic acid (fol); however, its relationship with other nutrients is not fully understood. We investigated the nutritional and genetic factors associated with HHcy and the possible dose-response relationships or threshold effects in patients in Northeast China. Genetic polymorphisms and micronutrients were tested with polymerase chain reaction and mass spectrometry, respectively. This trial was registered under trial number ChiCTR1900025136. The HHcy group had significantly more males and higher body mass index (BMI), methylenetetrahydrofolate reductase (MTHFR 677TT) polymorphism proportion, and uric acid, Zn, Fe, P, and vitamin A levels than the control group. After adjusting for age, sex, BMI, vitamin B12, fol, and MTHFR C677T, the lowest Zn quartile reduced the odds ratio of HHcy compared with the highest Zn quartile. The dose-response curves for the association between plasma Zn and HHcy were S-shaped. High plasma Zn concentrations were significantly correlated with high HHcy odds ratios, and the curve leveled off or slightly decreased. Most importantly, HHcy risk decreased with decreasing plasma Zn concentration; the threshold was 83.89 µmol/L. Conclusively, individuals residing in Northeast China, especially those with the MTHFR 677TT polymorphism, must pay attention to their plasma Zn and Hcy levels.

Examination of electronically mismatched Diels-Alder reaction by on-line mass spectrometry

RATIONALE

Electronically mismatched Diels-Alder reactions have gained much attention as an alternative pathway for C-C bond formation. To facilitate the development of facile organic transformations, mechanistic investigations are required. Spectroscopic methods (NMR, electron paramagnetic resonance and UV-visible) are normally adopted for mechanistic examinations, but further improvements in directly obtaining structural information of short-lived intermediates are encouraged. Herein, an electronically mismatched Diels-Alder reaction between indole and 1,3-cyclohexadiene was studied using in situ electrospray ionization mass spectrometry (in situ ESI-MS). Based on direct sampling and detection of the in situ ESI-MS without sample pretreatment, the structures and dynamics of important intermediates were examined on-line.

METHODS

A syringe-based photocatalytic reactor and in situ ambient MS (AMS) evaluation system was constructed for mechanism studies. The role of oxygen was confirmed via control reaction employed in the N₂ -bubbled system. The stepwise cation radical-based pathway and the [2 + 2] cycloaddition process were determined through a series of experiments, including solvent evaluation, MS/MS experiments and dynamic monitoring.

RESULTS

The dependence of the reaction on solvent polarity demonstrated that the reaction occurs via the formation of cation radicals, which were captured, identified and dynamically monitored via in situ ESI-MS. Without pre-separation, the intermediate of [2 + 2] cycloaddition was identified and the cycloaddition process was thereby determined to be the combination of [4 + 2] cycloaddition and [2 + 2] cycloaddition. In addition, oxygen was proved to act as an electron mediator for both catalyst Ru(bpz)₃ (PF₆ )₂ and radical cations.

CONCLUSIONS

The mechanism of an electronically mismatched Diels-Alder reaction was successfully deduced by in situ MS associated with a syringe-based photocatalytic reactor. The structures and dynamics of cation radicals, the effect of O₂ for the reaction and the detailed process of [2 + 2] cycloaddition have been well demonstrated. This work could not only promote the understanding and development of facile photocatalytic transformations, but also enlarge the application range of AMS in on-line monitoring.